To create a moist environment for wound healing, a hydrocolloid-sheet composed of alginate, chitin/chitosan and fucoidan (ACF-HS) has been developed as a functional wound dressing. ACF-HS gradually adsorbed medium without any maceration and the medium adsorption in vitro reached constant after 18 h. ACF-HS could effectively interact with and protect a healing-impaired wound in diabetic db/db mice, providing a good moist healing environment with exudate. Furthermore, the wound dressing could have other properties like ease of application and removal, and proper adherence. The aim of this study was to evaluate an accelerating effect of ACF-HS on wound healing for healing-impaired wounds in diabetic db/db mice. Round full-thickness skin defects (12 mm in diameter) were made on the back of db/db mice to prepare healing-impaired wounds. After applying ACF-HS to the wounds, the mice were later killed and histological sections of the wound were prepared. Histological examinations showed significantly advanced granulation tissue and capillary formations in the wounds treated with ACF-HS on days 4, 9 and 14 compared with those in commercially available hydrocolloid wound dressing and non-treatment (control). Thus, ACF-HS may serve as a new wound dressing for diabetic healing-impaired wounds.